This invention relates generally to voltage converter circuits and more particularly to voltage converters for use with light emitting diode (LED) displays.
The use of LED displays is finding wide application in electrical instrumentation. Typically, a decoder-driver circuit receives a data input in digital code, decodes the input, and drives the LED display in response thereto.
In such electrical instrumentation, a regulated DC voltage is required for operating the digital circuitry and a voltage regulator is employed with AC to DC voltage conversion means to provide the regulated DC voltage from an AC voltage source.
Some power dissipation is associated with use of a voltage regulator, and heretofore the power dissipation has been increased substantially by driving the LED display from the regulated voltage output. One suggested circuit modification for reducing the regulator current and attendant power loss is the use of a transformer with a center taped secondary winding and connecting the LED display to the center tap and a common circuit terminal (e.g., ground) thereby completely bypassing the voltage regulator. A separate power terminal is required for applying DC voltage to the decoder logic circuitry.
However, some commercially available decoder-driver circuits have a single power input terminal for both the LED display and decoder. Typical of such circuits is the Fairchild FCI 34511 CMOS Latch Decoder-Driver.